竹原纤维碱和酶处理的纤细化效果研究

用碱、漆酶、精练酶通过正交设计实验对竹原纤维进行纤细化处理,测定了处理后的竹原纤维细度变化率、木质素含量及强度。结果表明:精练酶去除木质素的效果比碱和漆酶处理好,木质素含量从原来的18.98%降为7.27%,处理后竹原纤维强度几乎没有损伤;碱去除木质素的效果比漆酶好,但强度损伤比漆酶处理大;生物酶脱胶方法有望成为竹原纤维脱胶加工的实际生产方法。     

Laccase-catalyzed conversion of natural and synthetic hormones from a municipal wastewater

The Trametes versicolor-derived laccase-catalyzed oxidation of natural estrogens (estrone--E1; 17beta-estradiol--E2; and estriol--E3) and a synthetic estrogen (17alpha-ethinylestradiol--EE2) was studied in synthetic water and municipal wastewater to optimize the process for steroid estrogen removal in wastewater. The optimal pH for each studied steroid estrogen oxidation was approximately 6 in synthetic water. This research also focused on the wastewater matrix effect on developed enzymatic treatment. At pH 7.0 and 25+/-1 degrees C, the experiments showed that the laccase-catalyzed system for the removal of steroid estrogens was not significantly affected by the municipal wastewater matrix. Laccase activity of 20 U/ml was sufficient to achieve complete removal of studied steroid estrogens in both synthetic water and municipal wastewater. Moreover, 1-hydroxy-benzotriazole, when used as a mediator, improved laccase-catalyzed system efficiency, thus decreasing the overall cost of the enzymatic system.     

Evidence of an active laccase-like enzyme in deepwater pink shrimp (Parapenaeus longirostris)

This paper demonstrates the presence of an active laccase-like enzyme from deepwater pink shrimp (Parapenaeus longirostris) using polyacrylamide gel electrophoresis. This enzyme was found in all anatomical parts of the deepwater pink shrimp, but particularly in the cephalothorax, and became active during the course of storage. Gel staining with laccase-specific substrates such as ADA, DMP and DAB was used to characterize a protein of around 44 kDa as containing laccase activity. The enzyme was inhibited by a specific inhibitor, CTAB. 4-Hexylresorcinol, a specific inhibitor of polyphenoloxidase (PPO), did not inhibit the laccase-like enzyme. Low concentrations of antioxidants ascorbic acid or sodium metabisulphite were sufficient to inhibit the laccase-like enzyme. ABTS and DMP were subsequently used to characterize the enzyme. Given the evidence of this enzyme in deepwater pink shrimp, new melanosis-inhibiting compounds that are suitable for consumption need to be found to complement specific inhibitors of PPO activity.     

Laccase-catalyzed removal of bisphenol-A from water: protective effect of PEG on enzyme activity

The feasibility of using the enzyme laccase to treat synthetic wastewater containing bisphenol-A (BPA) was examined. Optimization of pH, laccase concentration, polyethylene glycol (PEG) as an additive for >95% conversion and precipitation of BPA over 3 h of reaction period was determined through colorimetric assay and HPLC. PEG reduced enzyme inactivation, allowing a 5.2-fold reduction in the amount of laccase required for >95% removal of BPA in the range of 0.1-1 mM over 3 h. The fate of PEG after the reaction was also monitored. Linear relationships were found between the concentration of BPA (0.1-1 mM) and the optimum concentrations of laccase and PEG. Little PEG remained in the solution when up to 75 mg/L of PEG was used to treat 0.5 mM BPA. Beyond this level, PEG concentration increased linearly in the supernatant. It is inferred that an interaction between PEG and the polymeric products resulted in the protection of laccase.     

Well-ordered thin films as practical components of biosensors

A Langmuir-Blodgett (LB) film consisting of glutaraldehyde as the binding site for enzyme molecule, an amphiphilic N-alkyl-bis(thiophene)carbazole (BTC7) as the additional electron mediator, and 22-tricosenoic acid (TA) as the matrix for these molecules were deposited on a hydrophilic substrate. Laccase was then covalently immobilized on the film via glutaraldehyde (GA). The sensitivity of this sensor was about twice as high as that of laccase sensor prepared with the same LB film as above but without the bis(thiophene)carbazole derivative. The laccase LB film exhibited enzyme activity.     

Laccase immobilized on methylene blue modified mesoporous silica MCM-41/PVA

The mesoporous silica sieve MCM-41 containing methylene blue (MB) provides a suitable immobilization of biomolecule matrix due to its uniform pore structure, high surface areas, good biocompatibility and nice conductivity. Based on this, a facilely fabricated amperometric biosensor by entrapping laccase into the MB modified MCM-41/PVA composite film has been developed. Laccase from Trametes versicolor is assembled on a composite film of MCM-41 containing MB/PVA modified Au electrode and the electrode is characterized with respect to transmission electron microscopy (TEM) and scanning electron microscopic (SEM), Cyclic voltammetry (CV), response time, detection limit, linear range and activity of laccase. The laccase modified electrode remains good redox behavior in pH 4.95 acetate buffer solution, at room temperature in present of 0.1 mM catechol. The response time (t_90%) of the modified electrode is less than 4 s for catechol. The detection limit is 0.331 µM and the linear detect range is about from 4.0 µM to 87.98 µM for catechol with a correlation coefficient of 0.99913(S/N = 3). The apparent Michaelis–Menten (K_M^app) is estimated using the Lineweaver–Burk equation and the K_M^app value is about 0.256 mM. This work demonstrated that the mesoporous silica MCM-41 containing MB provides a novel support for laccase immobilization and the construction of biosensors with a faster response and better bioactivity.     

Effect of metal ions on reactive dye decolorization by laccase from Ganoderma lucidum

In this work, the influence of different metal ions on laccase activity and laccase-catalyzed dye decolorization was investigated under in vitro conditions using crude laccase obtained from a white rot fungus Ganoderma lucidum. Laccase activity was enhanced by metal ions such as Ca²⁺, Co²⁺, Cu²⁺ and Zn²⁺ at low concentrations (1 mM). Increasing the concentration of metal ions except that of Cu²⁺ and Zn²⁺ up to 5 mM and above decreased the enzyme activity. Among several heavy metals, Fe²⁺ highly inhibited the enzyme activity. Effect of metal ions was tested on decolorization of two reactive dyes, namely Remazol black-B (RB-5) and Remazol brilliant blue R (RBBR) at a concentration of 50 mg l⁻¹. The presence of heavy metals generally did not exert much influence on the decolorization except Fe²⁺. Cu²⁺ and Cr⁶⁺ enhanced the decolorization of both dyes. In the presence of 1 mM Cu²⁺, 94% of RB-5 and 35.5% of RBBR were decolorized during 1 h incubation. G. lucidum laccase was able to tolerate mixture of several metal ions. Treatment of simulated reactive dye effluent by laccase showed that the redox mediator system is necessary for effluent decolorization. Syringaldehyde, a natural redox mediator, was very effective than the synthetic mediator 1-hydroxybenzotriazole (HBT). The initial rate of effluent decolorization in presence of syringaldehyde (0.0831 h⁻¹) was 5.6 times higher than HBT (0.0152 h⁻¹). Although the rate of decolorization was markedly decreased in the effluent containing mixed metal ions, presence of syringaldehyde showed effective decolorization. This study indicates that G. lucidum laccase and natural redox mediator system could be a potential candidate for color removal from reactive dye effluent.     

Effect of Laccase and Xylanase Enzyme Treatment on Chemical and Mechanical Properties of Banana Fiber

This work analyses the effect of Laccase and Xylanase enzyme treatment on chemical and mechanical properties of banana fiber. Properties such as chemical composition, density, tensile strength, and color were analyzed. The removal of lignin increased with increase in enzymes concentration. Lignin removal was observed to be higher for Laccase treatment. The hemicellulose removal was higher for Xylanase treatment and the results were confirmed by FTIR spectrum. It is evident that cellulose%, density and tensile strength increased up to 15% enzyme treatment concentration and then started declining at 20% enzyme concentration in the case of both enzymes, whereas the moisture regain percentage of the fiber decreased with increase in enzyme concentration. The effects of enzymatic treatments are clearly visible in the SEM images.     

Crosslinking of interfacial layers in multilayered oil-in-water emulsions using laccase: Characterization and pH-stability

The enzymatic crosslinking of polymer layers adsorbed at the interface of oil-in-water emulsions was investigated. A sequential two step process, based on the electrostatic deposition of pectin onto a fish gelatin interfacial membrane was used to prepare emulsions containing oil droplets stabilized by fish gelatin-beet pectin membranes (citrate buffer, 10 mM, pH 3.5). First, a fine dispersed primary emulsion (5% soybean oil (w/v), 1% (w/w) gelatin solution) (citrate buffer, 10 mM, pH 3.5) was produced using a high pressure homogenizer. Second, a series of secondary emulsions were formed by diluting the primary emulsion into pectin solutions (0 - 0.4% (w/w)) to coat the droplets. Oil droplets of stable emulsions with different oil droplet concentrations (0.1%, 0.5%, 1.0% (w/v)) were subjected to enzymatic crosslinking. Laccase was added to the fish gelatin-beet pectin emulsions and emulsions were incubated for 15 min at room temperature. The pH- and storage stability of primary, secondary and secondary, laccase-treated emulsions was determined. Results indicated that crosslinking occurred exclusively in the layers and not between droplets, since no aggregates were formed. Droplet size increased from 350 to 400 nm regardless of oil droplet concentrations within a matter of minutes after addition of laccase suggesting formation of covalent bonds between pectin adsorbed at interfaces and pectin in the aqueous phase in the vicinity of droplets. During storage, size of enzymatically treated emulsions decreased, which was found to be due to enzymatic hydrolysis. Results suggest that biopolymer-crosslinking enzymes could be used to enhance stability of multilayered emulsions.